Olopatadine formulations for topical nasal administration

ABSTRACT

Topical formulations of olopatadine for treatment of allergic or inflammatory disorders of the nose are disclosed. The aqueous formulations contain approximately 0.6% (w/v) of olopatadine.

This application is a continuation-in-part of Ser. No. 11/079,996, filed Mar. 15, 2005, which is a continuation of Ser. No. 10/175,106, filed Jun. 19, 2002, which claims priority to U.S. Provisional Application Ser. No. 60/301,315, filed Jun. 27, 2001, all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to topical formulations used for treating allergic and inflammatory diseases. More particularly, the present invention relates to formulations of olopatadine and their use for treating and/or preventing allergic or inflammatory disorders of the nose.

2. Description of the Related Art

As taught in U.S. Pat. Nos. 4,871,865 and 4,923,892, both assigned to Burroughs Wellcome Co. (“the Burroughs Wellcome Patents”), certain carboxylic acid derivatives of doxepin, including olopatadine (chemical name: Z-11-(3-dimethylaminopropylidene)-6,11-dihydrodibenz[b,e]oxepine-2-acetic acid), have antihistamine and antiasthmatic activity. These two patents classify the carboxylic acid derivatives of doxepin as mast cell stabilizers with antihistaminic action because they are believed to inhibit the release of autacoids (i.e., histamine, serotonin, and the like) from mast cells and to inhibit directly histamine's effects on target tissues. The Burroughs Wellcome Patents teach various pharmaceutical formulations containing the carboxylic acid derivatives of doxepin, including nasal spray and ophthalmic formulations. See, for example, Col. 7, lines 7-26, and Examples 8 (H) and 8 (I) of the '865 patent.

U.S. Pat. No. 5,116,863, assigned to Kyowa Hakko Kogyo Co., Ltd., (“the Kyowa patent”), teaches that acetic acid derivatives of doxepin and, in particular, olopatadine, have anti-allergic and anti-inflammatory activity. Olopatadine is the cis form of the compound having the formula:

Medicament forms taught by the Kyowa patent for the acetic acid derivatives of doxepin include a wide range of acceptable carriers; however, only oral and injection administration forms are mentioned.

U.S. Pat. No. 5,641,805, assigned to Alcon Laboratories, Inc. and Kyowa Hakko Kogyo Co., Ltd., teaches topical ophthalmic formulations containing olopatadine for treating allergic eye diseases. According to the '805 patent, the topical formulations may be solutions, suspensions or gels. The formulations contain olopatadine, an isotonic agent, and “if required, a preservative, a buffering agent, a stabilizer, a viscous vehicle and the like.” See Col. 6, lines 30-43. “[P]olyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid or the like” are mentioned as the viscous vehicle. See Col. 6, lines 55-57.

PATANOL® (olopatadine hydrochloride ophthalmic solution) 0.1% is currently the only commercially available olopatadine product for ophthalmic use. According to its labelling information, it contains olopatadine hydrochloride equivalent to 0.1% olopatadine, 0.01% benzalkonium chloride, and unspecified amounts of sodium chloride, dibasic sodium phosphate, hydrochloric acid and/or sodium hydroxide (to adjust pH) and purified water.

Topical olopatadine formulations that are effective as products for treating allergic or inflammatory conditions in the nose are desirable.

SUMMARY OF THE INVENTION

The present invention provides topical olopatadine formulations that are effective as products for treating allergic or inflammatory disorders of the nose. The formulations of the present invention are aqueous solutions that comprise approximately 0.6% olopatadine. Despite their relatively high concentration of olopatadine, they do not contain any polymeric ingredient as a physical stability enhancing ingredient. The formulations contain a phosphate salt that permits the pH of the formulations to be maintained within the range 3.5-3.95 and that also aids in solubilizing the olopatadine drug in the presence of sodium chloride.

Among other factors, the present invention is based on the finding that stable, nasal spray, solution formulations of olopatadine can be prepared within a pH range of 3.5-3.95 using a phosphate buffer without the need for any polymeric ingredient to enhance the solubility or physical stability of the formulation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show the pH-solubility profile of olopatadine.

FIG. 2 shows the effect of NaCl and Na₂HPO₄ on the dissolution of olopatadine in water.

FIG. 3 shows the effect of NaCl and Na₂HPO₄ on the dissolution of olopatadine in a nasal vehicle.

FIG. 4 shows the effect of NaCl and Na₂HPO₄ concentrations on the dissolution rate of olopatadine in a nasal vehicle.

FIG. 5 shows the buffer capacity of an olopatadine nasal spray composition.

DETAILED DESCRIPTION OF THE INVENTION

Unless indicated otherwise, all component amounts are presented on a % (w/v) basis and all references to amounts of olopatadine are to olopatadine free base.

Olopatadine is a known compound that can be obtained by the methods disclosed in U.S. Pat. No. 5,116,863, the entire contents of which are hereby incorporated by reference in the present specification. The solution formulations of the present invention contain 0.54-0.62% olopatadine. Preferably, the solution formulations contain 0.6% olopatadine.

Olopatadine has both a carboxylic functional group (pKa₁=4.18) and a tertiary amino group (pKa₂=9.79). It exists in different ionic forms depending upon the pH of the solution. Olopatadine exists predominantly as a zwitterion in the pH range between the two pKa values with a negatively-charged carboxylic group and a positively-charged tertiary amino group. The iso-electric point of the olopatadine zwitterion is at pH 6.99. At a pH lower than pKa₁, cationic olopatadine (with ionized tertiary amino group) is dominant. At a pH higher than pKa₂, anionic olopatadine (with ionized carboxylic group) is dominant.

In many zwitterionic molecules, such as various amino acids, intra-molecular ionic interactions are not significant or do not exist. But the structure of olopatadine is such that intra-molecular interactions exist and are significant, possibly due to the distance and bonding angle between the oppositely charged functional groups. This interaction effectively reduces the ionic and dipole character of the molecule. The net effect of the intra-molecular interactions between the oppositely charged functional groups is the reduction of aqueous solubility of olopatadine. Olopatadine has the pH-solubility profile shown in FIGS. 1A (theoretical) and 1B (obtained using phosphate buffer).

Generally, olopatadine will be added in the form of a pharmaceutically acceptable salt. Examples of the pharmaceutically acceptable salts of olopatadine include inorganic acid salts such as hydrochloride, hydrobromide, sulfate and phosphate; organic acid salts such as acetate, maleate, fumarate, tartrate and citrate; alkali metal salts such as sodium salt and potassium salt; alkaline earth metal salts such as magnesium salt and calcium salt; metal salts such as aluminum salt and zinc salt; and organic amine addition salts such as triethylamine addition salt (also known as tromethamine), morpholine addition salt and piperidine addition salt. The most preferred form of olopatadine for use in the solution compositions of the present invention is the hydrochloride salt of (Z)-11-(3-dimethylaminopropylidene)-6,11-dihydro-dibenz-[b,e]oxepin-2-acetic acid. When olopatadine is added to the compositions of the present invention in this salt form, 0.665% olopatadine hydrochloride is equivalent to 0.6% olopatadine free base. Preferably the compositions of the present invention comprise approximately 0.665% olopatadine hydrochloride.

In addition to olopatadine, the aqueous solution compositions of the present invention comprise a phosphate salt. The phosphate salt not only helps maintain the pH of the compositions within the targeted pH range of 3.5-3.95 by contributing to the buffer capacity of the compositions, but also helps solubilize olopatadine. Suitable phosphate salts for use in the compositions of the present invention include monobasic sodium phosphate, dibasic sodium phosphate, tribasic sodium phosphate, monobasic potassium phosphate, dibasic potassium phosphate, and tribasic potassium phosphate. The most preferred phosphate salt is dibasic sodium phosphate. The compositions of the present invention comprise an amount of phosphate salt equivalent (on an osmolality contribution basis) to 0.2-0.8%, preferably 0.3-0.7%, and most preferably 0.4-0.6% of dibasic sodium phosphate. In a preferred embodiment, the phosphate salt is dibasic sodium phosphate at a concentration of 0.4-0.6% (w/v). In a most preferred embodiment, the compositions contain 0.5% (w/v) dibasic sodium phosphate.

Phosphate buffer is commonly used in aqueous pharmaceutical compositions formulated near neutral pH. Phosphate buffer (pKa₁=2.12, pKa₂=7.1, pKa₃=12.67) would not normally be chosen for an aqueous composition with a target pH range of 3.5-3.95 because it has low buffer capacity in that region. Other buffering agents are commonly used in aqueous pharmaceutical compositions, including acetate, citrate and borate buffers, but are not suitable for use in the topical nasal compositions of the present invention. Borate buffers are not suitable because they do not have any significant buffer capacity in the pH range 3.5-3.95. Though acetate and citrate buffers have buffer capacity in this region, they are not preferred because they have the potential to cause irritation to nasal mucosal tissues and undesirable taste and/or smell.

In addition to olopatadine and phosphate salt, the compositions of the present invention comprise sodium chloride as a tonicity-adjusting agent. The compositions contain sodium chloride in an amount sufficient to cause the final composition to have a nasally acceptable osmolality, preferably 240-350 mOsm/kg. Most preferably, the amount of sodium chloride in the compositions of the present invention is an amount sufficient to cause the compositions to have an osmolality of 260-330 mOsm/kg. In a preferred embodiment, the compositions contain 0.3-0.6% sodium chloride. In a more preferred embodiment, the compositions contain 0.35-0.55% sodium chloride, and in a most preferred embodiment, the compositions contain 0.35-0.45% sodium chloride.

The compositions of the present invention also contain a pharmaceutically acceptable pH-adjusting agent. Such pH-adjusting agents are known and include, but are not limited to, hydrochloric acid (HCl) and sodium hydroxide (NaOH). The compositions of the present invention preferably contain an amount of pH-adjusting agent sufficient to obtain a composition pH of 3.5-3.95, and more preferably, a pH of 3.6-3.8.

In one embodiment, the aqueous compositions of the present invention consist essentially of olopatadine, phosphate buffer, sodium chloride, a pH-adjusting agent, and water, and have a pH from 3.5-3.95. These compositions can be manufactured as sterile compositions and packaged in multi-dose, pressurized aerosol containers to avoid microbial contamination. In another embodiment, the aqueous compositions of the present invention contain a preservative and a chelating agent such that the compositions pass United States Pharmacopeia/National Formulary XXX criteria for antimicrobial effectiveness, and more preferably the Pharm. Eur. 5^(th) Edition criteria for antimicrobial preservation (Pharm. Eur. B preservative effectiveness standard). Suitable preservatives include p-hydroxybenzoic acid ester, benzalkonium chloride, benzododecinium bromide, and the like. Suitable chelating agents include sodium edetate and the like. The most preferred preservative ingredient for use in the compositions of the present invention is benzalkonium chloride (“BAC”). The amount of benzalkonium chloride is preferably 0.005-0.015%, and more preferably 0.01%. The most preferred chelating agent is edetate disodium (“EDTA”). The amount of edetate disodium in the compositions of the present invention is preferably 0.005-0.015%, and more preferably 0.01%.

The aqueous solution compositions of the present invention do not contain a polymeric ingredient intended to enhance the solubility of olopatadine or the physical stability of the solution. For example, the compositions of the present invention do not contain polyvinylpyrrolidone, polystyrene sulfonic acid, polyvinyl alcohol, polyvinyl acrylic acid, hydroxypropylmethyl cellulose, sodium carboxymethyl cellulose or xanthan gum.

The compositions of the present invention are preferably packaged in opaque plastic containers. A preferred container is a high-density polyethylene container equipped with a nasal spray pump. Preferably, the package is designed to provide the spray characteristics described in commonly-assigned, co-pending, U.S. Patent Application Publication No. 2006/0110328, which is incorporated herein by reference.

The present invention also relates to a method of treating allergic rhinitis comprising topically administering to the nasal cavities a composition containing 0.6% olopatadine, phosphate buffer, sodium chloride, a pH-adjusting agent, and water. The compositions optionally contain one or more preservative ingredients. Preferably, the compositions are administered such that 1200 mcg of olopatadine (e.g., 600/mcg per 100 microliter spray×two sprays) is delivered to each nostril twice per day.

Certain embodiments of the invention are illustrated in the following examples.

EXAMPLE 1 Topically Administrable Nasal Solution

TABLE 1 Ingredient Amount (%, w/v) Olopatadine Hydrochloride 0.665^(a) Benzalkonium Chloride 0.01 Edetate Disodium, Dihydrate 0.01 Sodium Chloride 0.41 Dibasic Sodium Phosphate, Anhydrous 0.5 Hydrochloric Acid Adjust to pH 3.7 ± 0.1 and/or Sodium Hydroxide Purified Water qs to 100 ^(a)0.665% w/v olopatadine hydrochloride (665 mcg/100 microliter spray) is equivalent to 0.6% w/v olopatadine as base (600 mcg/100 microliter spray). An exemplary compounding procedure for the nasal composition shown in Table 1 is described as below.

-   1. Tare a suitable compounding vessel with magnetic stir bar. Add     approximately 80% of the batch weight of purified water. -   2. While stirring, add dibasic sodium phosphate (anhydrous), sodium     chloride, edetate disodium, benzalkonium chloride and olopatadine     HCl. -   3. Add equivalent to approximately 0.55 g, 6N hydrochloric acid per     100 ml batch. -   4. Allow adequate time between each addition for dissolution of each     ingredient -   5. Add purified water to approximately 90% of final batch weight. -   6. Measure pH and adjust, if necessary, to 3.7 with 6N (and/or 1N)     hydrochloric acid and 1N sodium hydroxide. -   7. Adjust to final batch weight with purified water (QS). -   8. Measure final pH. -   9. Filter through 0.2 μm filtration membrane.

EXAMPLE 2 Effect of NaCl and Phosphate Buffer on Dissolution of Olopatadine Hydrochloride

The effect of NaCl on the dissolution rate of olopatadine hydrochloride in water was determined. NaCl caused a significant reduction in the rate of dissolution of olopatadine. With addition of Na₂HPO₄, however, the dissolution of olopatadine was dramatically improved. The complete dissolution of 0.6% olopatadine solution without Na₂HPO₄ would take at least several hours assuming that the entire amount of olopatadine would eventually dissolve, but with Na₂HPO₄ it takes less than one minute. The results are shown in FIG. 2.

EXAMPLE 3 Effect of NaCl and Na₂HPO₄ on the Dissolution Olopatadine Hydrochloride in a Nasal Vehicle

The effect of NaCl, Na2HPO4, and mannitol on the dissolution rate of olopatadine hydrochloride in a nasal formulation containing 0.01% EDTA and 0.01% BAC was determined. The results are shown in FIG. 3. The effect of phosphate salt in this vehicle is the same as that shown in water in Example 2.

EXAMPLE 4 Effect of NaCl and Na₂HPO₄ Concentrations on Dissolution

The effect of NaCl and Na₂HPO₄ concentrations on the dissolution rate of olopatadine hydrochloride in a nasal formulation containing 0.01% EDTA and 0.01% BAC was determined. The results are shown in FIG. 4. The aqueous solubility of olopatadine HCl decreases with increasing concentration of NaCl. However, increasing phosphate buffer correlates with increased aqueous solubility of olopatadine HCl in the presence of NaCl.

EXAMPLE 5 Effect of Phosphate Buffer on Olopatadine Nasal Spray Composition

The two compositions shown in Table 2 below were prepared using the procedure described in Example 1 and visual observations of the compositions clarity were made at different points during the compounding procedure. The results are shown in Table 2. TABLE 2 Formulation 2A Formulation 2B Component % w/v % w/v Olopatadine HCl 0.665 0.665 Benzalkonium Chloride 0.01 + 3% xs 0.01 + 3% xs Disodium EDTA 0.01 0.01 Sodium Chloride 0.37 0.7 Dibasic Sodium Phosphate 0.5 absent Sodium Hydroxide pH to 3.7 pH to 3.7 Hydrochloric Acid pH to 3.7 pH to 3.7 Purified Water qs 100 qs 100 Batch Size 2000 mL 2000 mL Osmolality 266 250 Initial pH 6.704 3.189 Final pH 3.699 3.618 Visual Observations: Upon addition of HCl Solution appeared clear with Solution appeared cloudy a few particles with many particles suspended After overnight stirring Solution became cloudy with Solution remained cloudy many particles with many particles Final pH adjustment Solution began to clear Solution remained cloudy during pH adjust down to 3.7 even after pH adjust down to 3.6 Add final batch quantity of water Solution remained clear Solution was still cloudy (approximately 10%) with many particles The results for Formulation A show that it is a clear solution. The results for Formulation B show that despite the pH-solubility profile indicating 0.6% olopatadine should dissolve at pH 3.189, the olopatadine did not go into solution. These results demonstrate that, without phosphate buffer, 0.665% olopatadine hydrochloride did not completely dissolve in water in the presence of 0.7% NaCl at a pH as low as 3.6 using the compounding procedure described in Example 1.

EXAMPLE 6 Effect of Phosphate Buffer Added to Cloudy 0.6% Olopatadine Nasal Spray Composition

Formulations 3A, 3B, and 3C shown in Table 3 were prepared without phosphate buffer and, despite extensive stirring, the olopatadine HCl was not completely solubilized. A portion of Formulation 3C was removed and phosphate buffer was added to form Formulation 3D. The results, summarized in Table 3, demonstrate that 0.665% olopatadine hydrochloride is not soluble in the tested nasal vehicle without a phosphate salt. TABLE 3 Formulation 3A Formulation 3B Formulation 3C Formulation 3D Olopatadine HCl 0.665 0.665 0.665 0.665 Benzalkonium 0.01 + 3% xs 0.01 + 3% xs 0.01 + 3% xs 0.01 + 3% xs Chloride Disodium EDTA 0.01 0.01 0.01 0.01 Sodium Chloride 0.33 0.7 0.7 0.7 Sodium pH to 3.7 pH to 3.7 pH to 3.7 pH to 3.7 Hydroxide Hydrochloric pH to 3.7 pH to 3.7 pH to 3.7 pH to 3.7 Acid Purified Water qs 100% qs 100% qs 100% qs 100% Batch Size 300 mL 800 mL 2000 mL 100 mL Osmolality 137 246 250 — Initial pH 3.002 3.176 3.189 6.908 Final pH 3.002 3.664 3.618 3.7 Visual Observations: Upon addition of Olopatadine HCl, Upon addition of Olopatadine HCl, Upon addition of Used dibasic sodium phosphate solution appeared cloudy, batch solution appeared cloudy, batch was Olopatadine HCl, (0.5%) in attempts to clarify a was qs to 100% and qs to 90% and pH adjusted, solution solution appeared portion of the cloudy solution still cloudy still cloudy cloudy (Formulation 3C) After 2.5 hours of stirring, solution After 7 hours of stirring, the After overnight Within a minute of stirring, the began to clear solution was still cloudy. stirring, the solution solution became clear with a few but still many particles* remained cloudy with particles** in solution (mostly in solution many particles* fibrous in appearance) After 3.5 hours of stirring, solution After 7 days of stirring, the solution After final qs to 100% After qs to 100% (using solution appeared clear with particles* was still cloudy with many particles* and pH adjust, the from the original batch), the solution was still solution remained clear with cloudy with a few fibrous particles** many particles* After overnight stirring, solution The batch was qs to 100% and still After approx. 7 hours appeared clear with several cloudy with of stirring, the solution particles* many particles* was cloudy with many particles* *Insoluble drug related **Extraneous fibrous particles

EXAMPLE 7 Effect of Compounding Sequence on 0.6% Olopatadine Nasal Spray Composition

The composition of Example 1 above was prepared using four different sequences for the addition of ingredients. The four sequences are indicated in Table 4 in the “OA” (order of addition) columns. In each case, visual observations relating to the composition's clarity were recorded. The results are shown in Table 4. In all four cases (Formulations 4A-4D), at the end of the compounding procedure, the solutions were clear. (The solutions contained some extraneous fibrous particles that did not appear to be related to the drug or the formulation excipients and were likely attributable to laboratory equipment and glassware.) TABLE 4 4A 4B 4C 4D Component % w/v OA^(a) % w/v OA^(a,c) % w/v OA^(a) % w/v OA^(a) Olopatadine HCl 0.665 3 0.665 5 0.665 2 0.665 2 Benzalkonium Chloride 0.01 4 0.01 4 0.01 3 0.01 4 Disodium EDTA 0.01 5 0.01 3 0.01 4 0.01 5 Sodium Chloride 0.41 6 0.41 2 0.41 5 0.41 6 Dibasic Sodium 0.5 1 0.5 1 0.5 6 0.5 1 Phosphate (Anhydrous) Sodium Hydroxide pH to 3.7 NA^(b) pH to 3.7 NA^(b) pH to 3.7 NA^(b) pH to 3.7 NA^(b) Hydrochloric Acid pH to 3.7 2 pH to 3.7 6 pH to 3.7 1 pH to 3.7 3 Purified Water qs 100% NA qs 100% NA qs 100% NA qs 100% NA Batch Size 100 mL 100 mL 100 mL 100 mL Sodium Hydroxide added 0.238 g (1N) None None None Hydrochloric Acid added 0.576 g (6N) 0.550 g (6N) 0.550 g (6N) 0.550 g (6N) Initial Observations Cloudy, many suspended Cloudy, many suspended Cloudy, many suspended Cloudy, many suspended particles particles particles particles Additional observations After 10 minutes - solution After 1 minute - clear with After 2 minutes - clear with a After 5 minutes - clear with a began to clear, many several suspended particles few suspended particles few suspended particles suspended particles After 30 minutes - clear with After 6 minutes - clear with a After 7 minutes - clear with a After 20 minutes - clear with several suspended particles few suspended particles few suspended particles a few suspended particles After 1 hour - clear with many After 1 hour - clear with a few After 1 hour - clear with After 1 hour - clear with suspended particles* suspended particles* several suspended particles* several suspended particles* Next day (approx 16 hours) - Next day (approx 16 hours) - Next day (approx 16 hours) - Next day (approx 16 hours) - clear with several particles* clear with a few particles* clear with a few particles* clear with a few particles* pH 3.698 3.692 3.718 3.724 Osmolality 274 283 279 280 ^(b)NA = not applicable ^(c)Preferred method of manufacturing *Extraneous fibrous particles

EXAMPLE 8 Effect of Various Buffer Systems

The composition of Example 1 above was prepared but acetate, borate and citrate buffers, respectively, were substituted in place of the phosphate buffer. Visual observations regarding the clarity of each of the compositions were recorded and are shown in Table 5. TABLE 5 5A 5B 5C Component % w/v Olopatadine HCl 0.665 0.665 0.665 Benzalkonium 0.01 0.01 0.01 Chloride Disodium EDTA 0.01 0.01 0.01 Sodium Chloride 0.41 0.41 0.41 Sodium Acetate 0.5 — — Sodium Borate — — 0.5 Sodium Citrate — 0.5 — Sodium Hydroxide pH to 3.7 pH to 3.7 pH to 3.7 Hydrochloric Acid^(a) pH to 3.7 pH to 3.7 pH to 3.7 Purified Water qs 100% qs 100% qs 100% Batch Size 100 mL 100 mL 100 mL Sodium Hydroxide 0.332 g (1N) 0.244 g (1N) 0.963 g (1N) added Hydrochloric Acid 0.550 g (6N) 0.550 g (6N) 0.550 g (6N) added pH 3.711 3.710 3.716 Osmolality 257 246 270 Visual Observations: Observations: Initial Upon addition of Upon addition of Upon addition of Olopatadine, batch Olopatadine, batch Olopatadine, batch appeared cloudy but appeared cloudy but appeared cloudy but began to clear within a began to clear within began to clear with in a few seconds one minute few seconds Additional After 3 minutes of After 17 minutes of After 16 minutes of observations: stirring, solution stirring, solution stirring, solution appeared clear with a appeared clear with appeared clear with a few extraneous particles several large flakey few large flakey particles particles After 20 additional After 20 additional After 20 additional minutes of stirring, minutes of stirring, minutes of stirring, solution appeared clear solution appeared clear solution appeared clear with very few with very few with very few extraneous particles extraneous particles extraneous particles The pH was adjusted, The pH was adjusted, The pH was adjusted, solution was brought to solution was brought to solution was brought to 100% of batch weight 100% of batch weight 100% of batch weight and remained clear (with and remained clear (with and remained clear (with very few extraneous very few extraneous very few extraneous particles) particles) particles)

EXAMPLE 9 Effect of Phosphate Buffer, NaCl, and Hot Water

The compositions shown in Table 6 were prepared to examine (1) the effect of adding phosphate buffer to a composition containing olopatadine hydrochloride, BAC, EDTA, NaOH/HCl, and NaCl, (2) the effect of adding NaCl to a composition containing olopatadine, BAC, EDTA, NaOH/HCl, and (3) the effect of hot water on the dissolution of olopatadine in a composition comprising olopatadine, BAC, EDTA, NaCl and NaOH/HCl. In each case, visual observations concerning the clarity of the composition were recorded. The results are shown in Table 6. TABLE 6 Component 6A1 6A2 6B1 6B2 6C* Olopatadine HCl 0.665 (3)  Same 0.665 (3)  Same 0.665 (4)  Benzalkonium 0.01 (5) Same 0.01 (2) Same 0.01 (3) Chloride Disodium EDTA 0.01 (4) Same 0.01 (1) Same 0.01 (2) Sodium Chloride  0.8 (1) Same — Added 0.8% to existing  0.8 (1) solution Dibasic Sodium — Added 0.5% to existing — — — Phosphate solution Sodium 2 drops added (2) Same — Same pH to 3.7 Hydroxide qs pH to 3.7 (6) Purified Water qs 100% Same qs 100% Same qs 100% Batch Size 50 mL 25 mL 50 mL 25 mL 50 mL Initial pH 3.329 — 2.838 — 2.873 1N NaOH added 0.087 g — 0.343 g — 0.318 g Final pH 3.667 — 3.730 — 3.714 Observations: Upon addition of 25 mL portion of batch Upon addition of 25 mL portion of batch Upon addition of olopatadine HCl, solution 1 - phosphate added and olopatadine HCl, solution 2 - NaCl added and olopatadine HCl, the appeared cloudy with allowed to stir. Within 10 appeared cloudy with allowed to stir. After solution appeared cloudy many small white minutes, the solution many small white 10 minutes of stirring, with many white suspended particles appeared clear suspended particles the solution remained suspended particles clear After addition of EDTA After one day without After 2 minutes of After one day without After 5 minutes of and BAC, the solution stirring, solution stirring, the solution stirring, solution stirring, the solution appeared the same appeared clear with a began to clear, still with appeared clear with 2 began to clear, still with few extraneous fibers few many white particles small white flakey many small white (7:30 am) particles and a few suspended particles extraneous fibers (7:30 am) pH was adjusted to 3.7 Later that day (2:45 pm) After 5 additional Later that day (2:45 pm) After 20 minutes of and allowed to stir for 30 batch was observed to be of stirring, the solution the batch appeared clear stirring, the solution minutes, appearance was clear with many crystals was clear with very few (˜3-4) remained clear with the same formed at the bottom of small white flakey many small white the beaker particles and a few suspended particles extraneous fibers After one day without Next day (8:00 am), After pH adjust and qs to Next day (8:00 am), the After 30 additional stirring, the solution batch remained the same 100%, the batch batch remained the same minutes of stirring, the appeared clear with many remained clear solution remained the small white particles at same the bottom of the beaker (7:30 am) Next day (8:00 am), After one day without After pH adjust and qs to batch remained the stirring, the solution 100%, the solution was same. remained clear (7:30 am) allowed to stir and appeared the same Next day (8:00 am) batch After one day without remained the same stirring, the solution appeared clear with many small white particles settled at the bottom of the beaker Note: Number in parenthesis refers to order of addition of components. *Hot purified water (˜70° C.) was used.

EXAMPLE 10 Buffer Capacity of Phosphate Buffer

The contribution of phosphate buffer to the buffer capacity of the composition of Example 1 was determined in a classical acid-base titration experiment. The results are shown in FIG. 5. The buffer capacity of the composition of Example 1 (without phosphate buffer) was 2.66 from pH 3.5-3.8 and 2.7 from pH 3.5-3.9. The buffer capacity of the composition of Example 1 (i.e., including phosphate buffer) was 2.93 from pH 3.5-3.8 and 3.1 from pH 3.5-3.8.

EXAMPLE 11 Stability of Olopatadine Nasal Spray Compositions Lacking Phosphate Buffer

The compositions (without phosphate buffer) shown below in Table 7A were prepared. Visual observations of the clarity of each composition were recorded as each composition was prepared. The results are shown in Table 7A. TABLE 7A 7A 7B 7C Component % w/v Olopatadine HCl 0.665 (2) 0.665 (4)  0.665 (5)  Benzalkonium — 0.01 (3) 0.01 (4) Chloride Disodium EDTA — 0.01 (2) 0.01 (3) Sodium Chloride  0.8 (3)  0.8 (5)  0.8 (2) Sodium Hydroxide Adjust pH to 3.95 Adjust pH to 3.95 Adjust pH to 3.95 Hydrochloric Acid Adjust pH to 3.95 Adjust pH to 3.95 Adjust pH to 3.95 Purified Water qs 100% (1) qs 100% (1) qs 100% (1) Batch Size 200 ml 200 mL 200 mL Osmolality 286 286 n/a Initial pH 2.898 2.930 3.098 Final pH 3.947 3.952 3.957 Observations: Upon addition of drug, the solution Upon addition of drug, solution appeared Upon addition of drug, the solution appeared cloudy with many large flakey cloudy with many large flakey particles; appeared cloudy with many large flakey particles, after approx 20 minutes, the within approx 25 minutes, solution particles. After 3 hours of stirring the solution appeared clear with very few appeared clear with very few fibrous/small solution remained cloudy with many fibrous/small white particles (pH 2.845) white particles (pH 2.880) suspended particles Upon addition of NaCl, solution remained Upon addition of NaCl, solution remained After pH adjust and final qs, the solution the same (pH 2.898) the same (pH 2.930) remained cloudy with many suspended After pH adjust, final qs and several After pH adjust, final qs and several particles (while stirring) minutes of stirring, the final solution minutes of stirring, the final solution appeared clear with some fibrous appeared clear with some fibrous particles and a few small white particles and a few small white particles particles Note: Numbers in parenthesis next to the components represents the order of addition.

Each of the compositions was then split. One portion of each was split again into three storage batches (“pre-filtration”) and the other portion was filtered through a 0.2 μM filter and then split into three storage batches (“post-filtration”). One of the storage batches of each set was stored at room temperature (˜22° C.), one in the refrigerator (˜4° C.), and one subjected to freeze-thaw cycling (one day in the freezer (˜−20° C.) and one day at room temperature, except over the weekends). Visual observations of the clarity of each sample of Formulation 7A (lacking BAC and EDTA) were recorded on the indicated days and the results were recorded. The results are shown in Tables 7B (pre-filtration) and 7C (post-filtration). TABLE 7B 7A Pre-Filtration Observations: Bottle 1 (at RT) Bottle 2 (at 4° C.) Bottle 3 (at FTC^(a)) Initial Clear, many fibrous particles, a few Clear, many fibrous particles, a few Clear, many fibrous particles, a few small white particles small white particles small white particles Day 1 Clear, some fibrous particles, a few Same FT Cycle 1 - same small white particles Day 2 Same Same FT Cycle 2 - same Day 5 Clear, many fibrous particles, some Same FT Cycle 3 - same small white particles Day 6 Same Same FT Cycle 4 - same Day 7 Same Same FT Cycle 5 - same Day 8 Same Same FT Cycle 6 - Clear, many fibrous and Day 9 Same Same small white particles Day 12 Same Clear, many fibrous and some small white particles, crystallization on bottom/sides of vial Day 13 Same Same Day 14 Clear, many fibrous and small white Same particles (more than previous) A portion of the pre-filtered solution was transferred into three 20 mL glass vials and placed at the respective storage conditions for visual observation. ^(a)Freeze-thaw cycle performed at 24 hour freeze/24 hour thaw except over weekends.

TABLE 7C 7A Post-filtration Observations Bottle 1 (at RT) Bottle 2 (at 4° C.) Bottle 3 (at FTC^(a)) Initial Clear, very few fibrous particles Clear, very few fibrous particles Clear, very few fibrous particles Day 1 Clear, a few fibrous particles, Same FT Cycle 1 - Clear, few fibrous particles, one small white particle few small white particles Day 2 Same Clear, a few fibrous particles, some small FT Cycle 2 - Clear, few fibrous particles, white particles very few small white particles Day 5 Clear, a few fibrous particles Clear, a few fibrous particles, very few FT Cycle 3 - same small white particles Day 6 Same Same FT Cycle 4 - same Day 7 Same Same FT Cycle 5 - same Day 8 Same Same FT Cycle 6 - same Day 9 Same Same Day 12 Same Same Day 13 Same Same Day 14 Same Clear, a few fibrous and small white particles Note: A portion of the twice-filtered solution was transferred into three 50 mL media bottles and placed at the respective storage conditions for visual observation. ^(a)Freeze-thaw cycle performed at 24 hour freeze/24 hour thaw except over weekends.

After nine days of observation, the post-filtration portion of Formulation 7A was split and a stir bar was added to each sample as a seeding agent (the stir bar was not rotating). Visual observations were recorded and the results are shown in Table 7 D. TABLE 7D 7A Post-filtration Bottle 1 (at RT) Bottle 3 (at 4° C.) Bottle 5 (at FTC^(a)) Observations With Stir Bar Added As a Seeding Agent Initial^(b) Clear, a few fibrous particles Clear, a few fibrous particles Clear, a few fibrous particles Day 3 Same Clear, a few fibrous particles, very few FT Cycle 1 - Clear, a few fibrous small white particles particles, very few small white particles Day 4 Same Same FT Cycle 2 - same Day 5 Same Same ^(a)Freeze-thaw cycle performed at 24 hour freeze/24 hour thaw except over weekends. ^(b)Initial observations were performed prior to addition of stir bars.

To other portions of composition 7A split after nine days of observation, excess olopatadine (a few small granules) was added to both the pre-filtration and post-filtration samples to determine if seeding would cause olopatadine to precipitate. Visual observations were recorded on the indicated days. The results are shown in Tables 7 E (unfiltered composition) and 7 F (filtered composition). TABLE 7E 7A Pre-filtration (with excess olopatadine HCl) Observations Bottle 1 (at RT) Bottle 2 (at FTC^(a)) Initial^(b) Clear, many fibrous Clear, many fibrous particles, particles, some small white some small white particles particles Day 3 Clear, many fibrous/small FT Cycle 1 - clear, many white particles (powdery fibrous/small white particles settling) (powdery settling) Day 4 Same FT Cycle 2 - same Day 5 Same ^(a)Freeze-thaw cycle performed at 24 hour freeze/24 hour thaw except over weekends. ^(b)Initial observations were performed prior to addition of excess olopatadine HCl.

TABLE 7F 7A Post-filtration Bottle 2 (at RT) Bottle 4 (at 4° C.) Bottle 6 (at FTC^(a)) Observations With Excess Olopatadine HCl Added (1-2 small granules) Initial^(b) Clear, a few fibrous particles Clear, a few fibrous particles Clear, a few fibrous particles Day 3 Clear, many fibrous and small white Clear, many fibrous and small white FT Cycle 1 - Clear, many particles particles (powdery at bottom of vial, fibrous/small white particles (powdery settling) at bottom of vial, settling) Day 4 Same Same FT Cycle 2 - same Day 5 Same Same A portion of the solutions that had been through nine days of observations at RT and 4° C. and four FT cycles were transferred into three 20 mL glass vials and spiked with olopatadine HCl. These units were then placed at the respective storage conditions for visual observation. ^(a)Freeze-thaw cycle performed at 24 hour freeze/24 hour thaw except over weekends. ^(b)Initial observations were performed prior to addition of excess olopatadine HCl.

The stability of the composition “7B” (containing BAC and EDTA) was evaluated in the same fashion. The results are shown in Tables 7G (Pre-filtration), 7H (Post-filtration), 7I (with stir bar added after 9 days), 7J (with excess olopatadine added after 9 days; pre-filtration), and 7K (with excess olopatadine added after 9 days; post-filtration). TABLE 7G 7B Pre-filtration Observations: Bottle 1 (at RT) Bottle 2 (at 4° C.) Bottle 3 (at FTC^(a)) Initial Clear, many fibrous particles, a few Clear, many fibrous particles, a few Clear, many fibrous particles, a few small white particles small white particles small white particles Day 1 Clear, some fibrous particles, small Same FT Cycle 1 - Same white particles Day 2 Same Same FT Cycle 2 - Same Day 5 Clear, many fibrous particles, some Same FT Cycle 3 - Same small white particles Day 6 Same Same FT Cycle 4 - same Day 7 Same Same FT Cycle 5 - same Day 8 Same Same FT Cycle 6 - Clear, many fibrous and Day 9 Same Same small white particles Day 12 Same Same Day 13 Same Same Day 14 Clear, many fibrous and small white Same particles (more than previous) A portion of the pre-filtered solution was transferred into three 20 mL glass vials and placed at the respective storage conditions for visual observation. ^(a)Freeze-thaw cycle performed at 24 hour freeze/24 hour thaw except over weekends.

TABLE 7H 7B Post-filtration Observations Bottle 1 (at RT) Bottle 2 (at 4° C.) Bottle 3 (at FTC^(a)) Initial Clear, very few fibrous particles Clear, very few fibrous particles Clear, very few fibrous particles Day 1 Clear, a few fibrous particles Same FT Cycle 1 - Clear, few fibrous particles, few small white particles Day 2 Same Clear, a few fibrous particles, some small FT Cycle 2 - Clear, few fibrous particles, white particles very few small white particles Day 5 Same Clear, a few fibrous particles, very few FT Cycle 3 - same small white particles Day 6 Same Same FT Cycle 4 - same Day 7 Same Same FT Cycle 5 - same Day 8 Same Same FT Cycle 6 - same Day 9 Same Same Day 12 Same Clear, a few fibrous and small white particles (more than previous) Day 13 Same Clear, a few fibrous/small white particles, light layer of crystallization forming on bottom/sides of bottle Day 14 Same Same Note: A portion of the twice-filtered solution was transferred into three 50 mL media bottles and placed at the respective storage conditions for visual observation. ^(a)Freeze-thaw cycle performed at 24 hour freeze/24 hour thaw except over weekends.

TABLE 7I 7B Post-filtration Bottle 7 (at RT) Bottle 9 (at 4° C.) Bottle 11 (at FTC^(a)) Observations With Stir Bar Added Initial^(b) Clear, a few fibrous particles Clear, a few fibrous particles Clear, a few fibrous particles Day 3 Clear, a few fibrous particles, very few Clear, a few fibrous and small white FT Cycle 1 - Clear, a few fibrous small white particles particles particles, very few small white particles Day 4 Same Clear, a few fibrous/small white FT Cycle 2 - Clear, a few fibrous and particles, powdery at bottom of vial, small white particles settling Day 5 Same Clear, settling on bottom, many very fine white particles Note: A portion of the solutions that had been through nine days of observations at RT and 4° C. and four FT cycles were transferred into three 20 mL glass vials with stir bars added and placed at the respective storage conditions for visual observation. ^(a)Freeze-thaw cycle performed at 24 hour freeze/24 hour thaw except over weekends. ^(b)Initial observations were performed prior to addition of stir bars.

TABLE 7J Obser- 7B Pre-filtration (with excess olopatadine HCl) vations Bottle 3 (at RT) Bottle 4 (at FTC^(a)) Initial^(b) Clear, many fibrous particles, Clear, many fibrous particles, some small white particles some small white particles Day 3 Clear, many fibrous/small FT Cycle 1 - clear, many white particles (light powdery fibrous/small white particles settling) (powdery settling) Day 4 Same FT Cycle 2 - same Day 5 Same A portion of the pre-filtered solutions that had been through nine days of observations at RT and 4° C. and four FT cycles were transferred into three 20 mL glass vials and spiked with olopatadine HCl. The units were then placed at the respective storage conditions for visual observation. ^(a)Freeze-thaw cycle performed at 24 hour freeze/24 hour thaw except over weekends. ^(b)Initial observations were performed prior to addition of excess olopatadine HCl.

TABLE 7K 7B Post-filtration Bottle 8 (at RT) Bottle 10 (at 4° C.) Bottle 12 (at FTC^(a)) Observations With Excess Olopatadine Added (1-2 small granules) Initial^(b) Clear, a few fibrous particles Clear, a few fibrous particles Clear, a few fibrous particles Day 3 Clear, many fibrous and small white Clear, many fibrous and small white FT Cycle 1 - Clear, many particles particles (powdery at bottom of vial, fibrous/small white particles (powdery settling) at bottom of vial, settling) Day 4 Same Clear, many fibrous/small white FT Cycle 2 - same particles, crystallization at bottom of vial Day 5 Same Same A portion of the solutions that had been through nine days of observations at RT and 4° C. and four FT cycles were transferred into three 20 mL glass vials and spiked with olopatadine HCl. These units were then placed at the respective storage conditions for visual observation. ^(a)Freeze-thaw cycle performed at 24 hour freeze/24 hour thaw except over weekends. ^(b)Initial observations were performed prior to addition of excess olopatadine HCl.

EXAMPLE 12 Effect of Phosphate Buffer

The compositions shown below in Table 8 were prepared using a compounding procedure similar to that described in Example 1. In all four cases, the NaCl was added after olopatadine during the compounding. All four compositions contained the equivalent of 110% of a 0.6% targeted concentration. Two of the compositions were formulated at a pH of 3.95 and two at 4.10 to test an extreme condition. The results are shown in Table 8. TABLE 8 Formulation 12A Formulation 12B Formulation 12C Formulation 12D % (w/v) % (w/v) % (w/v) % (w/v) Olopatadine HCl 0.732 0.732 0.732 0.732 Benzalkonium Chloride 0.01 0.01 0.01 0.01 Disodium EDTA 0.01 0.01 0.01 0.01 Sodium Chloride 0.41 0.41 0.8 0.8 Dibasic Sodium Phosphate, 0.5 0.5 — — Anhydrous Sodium Hydroxide pH to 3.95 pH to 4.10 pH to 3.95 pH to 4.10 Hydrochloric Acid pH to 3.95 pH to 4.10 pH to 3.95 pH to 4.10 Purified Water qs 100% qs 100% qs 100% qs 100% Visual Observations: Initial Clear solution Clear solution Clear solution Clear solution Room Temperature (4 days) Remained clear Remained clear Remained clear Remained clear 4° C. (4 days) Remained clear on Remained clear on days 1, 2, Remained clear on days 1, 2, 3, Remained clear on days 1, 2, days 1, 2, 3 and 4. No and 3. On day 4, a very small and 4. No precipitate was and 3. On day 4, a significant precipitate was found. amount of clear crystals found. amount of clear crystals formed formed at the bottom of at the bottom of the glass vial. the glass vial. Comparing the results of Formulations B and D demonstrates that compositions with phosphate buffer are more stable against crystal formation than compositions without phosphate buffer.

EXAMPLE 13 Storage Stability

The solution stability of the composition of Example 1 was examined by preparing variations of the composition at the pH's shown in Table 9 and subjecting the samples to 13 freeze-thaw cycles (same cycles as described in Example 11 above). Following the last cycle, the samples were stored in the freezer for approximately three weeks and then analyzed. The amount of olopatadine (pre- and post-filtration, 0.2 μM filter) was determined by HPLC assay as a percent of the labeled amount (0.6%). The samples were evaluated using four tests of solution clarity: “Nephelos” values were obtained using a turbidimeter (HF Scientific, Inc., Model No. DRT100B); “Clarity” was determined by visual observation using a method similar to the Ph. Eur. (5^(th) Edition) method for evaluating solution clarity and degree of opalescence; “Precipitate” was determined by visual inspection and the presence of absence of precipitates was recorded; “Particles by Visual Observation” was determined by visual inspection under a light box where not more than 3 particles per 5 mL sample is considered “essentially particle free.” Osmolality and pH were also determined for each composition. The results are shown in Table 9. In four of the five cases (Samples 1-4), the compositions were clear solutions following the freeze-thaw cycling study, demonstrating the composition of Example 1 is a stable aqueous solution despite the absence of a polymeric physical stability-enhancing agent. The sample that did not remain a clear solution is Sample 5 (pH=4.45). TABLE 9 Olopatadine Assay Pre filtration Physical Test Results (% of label) Particles by Pre- Post- Nephelos¹ Visual Osmolality Sample Lot Filtration Filtration (In NTU) Clarity Precipitate Observation mOsm/Kg pH 1 99 100 0.3 Clear, None Essentially 280 3.83 99 99 NMT particle-free EP1 2 99 100 0.2 Clear, None Essentially 288 3.94 97 99 NMT particle-free EP1 3 100  101 0.2 Clear, None Essentially 285 4.01 98 99 NMT particle-free EP1 4  98, 98 0.5 Clear, None Essentially 287 4.15  99, 99 NMT particle-free EP1 5 98 98 (a) Crystal Clear, None Essentially 294 4.45 98 98 Form In one NMT particle-free Test Tube EP1 (b) Other test tube clear (0.6, 0.5)² ¹Nephelos (Turbidity) of ≦3 NTU is considered clear solution as per Ph. Eur. (5^(th) Ed.) ²Pre and post olopatadine assay, nephalos, clarity, precipitate, particles by visual observation, osmolality and pH were performed using clear solution from second test tube.

This invention has been described by reference to certain preferred embodiments; however, it should be understood that it may be embodied in other specific forms or variations thereof without departing from its special or essential characteristics. The embodiments described above are therefore considered to be illustrative in all respects and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description. 

1. A composition consisting essentially of a) 0.54-0.62% (w/v) olopatadine free base or an equivalent amount of a pharmaceutically acceptable salt of olopatadine; b) a phosphate salt in an amount equivalent to 0.2-0.8% (w/v) dibasic sodium phosphate, wherein the phosphate salt selected from the group consisting of monobasic sodium phosphate; dibasic sodium phosphate; tribasic sodium phosphate; monobasic potassium phosphate; dibasic potassium phosphate; and tribasic potassium phosphate; c) 0.3-0.6% (w/v) NaCl; d) a pH-adjusting agent in an amount sufficient to cause the composition to have a pH of 3.6-3.8; e) 0.005-0.015% (w/v) benzalkonium chloride; f) 0.005-0.015% (w/v) edetate disodium; and g) water.
 2. A composition consisting essentially of a) 0.6% (w/v) olopatadine free base or an equivalent amount of a pharmaceutically acceptable salt of olopatadine; b) 0.4-0.6% (w/v) dibasic sodium phosphate; c) 0.35-0.45% (w/v) NaCl; d) a pH-adjusting agent in an amount sufficient to cause the composition to have a pH of 3.6-3.8, wherein the pH-adjusting agent is selected from the group consisting of NaOH and HCl; e) 0.01% (w/v) benzalkonium chloride; f) 0.01% (w/v) edetate disodium; and g) water. 